Charlie Gibson’s last day in the “World News” anchor chair will be Dec. 18 — and ABC seems hell-bent on mak ing the transition to Diane Sawyer as low-key as possi ble (avoiding the hoo-ha that accompanied Katie Couric’s ascension to the “CBS Eve ning News” throne). Gibson leaves during the holiday sea son (which helps), and ABC won’t say when Sawyer starts her “World News” run — though it’s widely expected to be Monday, Dec. 21.

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Some more from my inter view with William Shatner, who kicks off the second sea son of “Shatner’s Raw Nerve” Sunday on BIO. I asked Shatner about reports he was angry at not being in vited to former “Star Trek” co-star George Takei’s wed ding to Brad Altman.

“I was joking about that one,” Shatner said. “I feel sorry for George, actually, be- cause of all these [negative] feelings [toward me] he seems to have. I’ve tried to have him on [‘Raw Nerve’]. I called him. I begged him. I told him, ‘There’s not much time left for anybody, why are you car rying on like this?’ ” Shatner is 78; Takei is 72.

BIO’s sister network, A&E, scored some nice numbers Monday night with the sea son premieres of “Interven tion” (2.5 million viewers) and “Hoarders” (3.2 million viewers and season-opening records in adults 18-49/ 25-54).

More: Cartoon Network’s “Ben 10: Alien Swarm” snared over 4 million viewers last Wednesday, that day’s top show in all kids and boy demos (broadcast and cable). The “Alien Swarm” DVD hit stores yesterday.